The major effort of this grant supported research is in the ultrastructural correlation of gastric acid secretion with gastric parietal cell ultrastructural analysis. The studies proposed for the next year includee the elucidation of the course and continuity of the intracellular or secretory canaliculus of the parietal cell during different states of secretion. A related aspect to this study is to determine the morphology of the parietal cell under conditions of maximal stimulated acid secretion. Finally a comprehensive morphometric study on the ratio of membrane distribution in the parietal cell in known states of acid secretion will be made. In this approach the relative distribution of membranes will be compared with the actual amount of membranes by using the mitochondria as a reference standard. Work on the enteric surface coat will involve the study of glycoprotein turnover or stability by labeling the living intestinal epithelial cell surface with cationized ferritin. Preliminary studies indicate that the turnover of labeled fuzzy surface coat material is not uniform and may be more rapid than indicated by other methods. BIBLIOGRAPHIC REFERENCES: L.J. Romrell, M. R. Munro, and S. Ito. Isolation and separation of highly enriched fractions of viable mouse gastric parietal cells by velocity sedimentation. J. Cell Biol. 65:428-438, 1975. Olden, D., S. Ito, T. H. Wilson. D-Alanine-requiring cell wall mutant of Escherichia coli. J. Bacteriology 122: 1310-1321, 1975.